In many instances, it is useful to provide an oven that cooks or heats food products by using steam. Specific uses of such steam ovens may vary, but one particular use is on board aircraft or other transportation vehicles in order to provide a quick, safe, and convenient method for cooking, heating, or re-heating food products.
Some existing steam ovens generate steam by injecting water directly or indirectly onto heating elements of the oven. In some systems, the water is injected inside a warm oven in a mist form, and when the water mist contacts the heating elements or the fan, the mist vaporizes instantly and becomes steam. Such systems are referred to as injection systems. One downside associated with injection systems is that over time, water calcification can build up on the heating elements and fan elements. A further downside of these systems is that the user needs to wait until the oven reaches a certain temperature before the water can be injected with the desired effects, which may take longer than is often desired.
Additionally, systems using these methods are typically pressurized systems, meaning that pressure must be built up and maintained inside the oven. Pressurized steam oven systems require additional safety precautions, such as tighter seals, more robust door construction, and additional safety features in order to prevent opening of the door while the oven is pressurized. They also tend to be more expensive, heavier, and create more liability during use. For example, when the user is ready to open the door, the pressure in the oven must be completely relieved before the door can be opened; opening the door in the middle of a cooking cycle can be quite dangerous, resulting in scalding the user or others in the vicinity. Additionally, pressurized steam ovens cannot be used if the seals are weakened or damaged or otherwise show signs of wear, adding to maintenance expense.
Other available steam ovens generate steam by dripping water into a recessed tray at the base of the oven. The recessed tray is heated by a second heating element positioned below the tray. Such systems are referred to as drip systems. One downside associated with drip systems is that due to the use of two heaters, they generate more heat loss from the unit, they require more power consumption, and they tend to be heavier than other types of steam ovens. Such systems are typically unpressurized ovens, which means that pressure is not maintained inside the oven. The cooking compartment may be opened at any time during the cooking process in order to check the oven without waiting for depressurization, which is considered by many to be less of a potential hazard than pressurized systems.
In many domestic and industrial steam ovens, separate steam generators are placed outside the cooking chamber. These steam ovens are fitted with a completely separate, external steam generator, which can be located in a separate compartment next to the oven or mounted directly to the inner lining of the oven. The steam from the external steam generator may be injected into the oven when needed, with the steam being heated to the desired temperature. These ovens do not lend themselves to use onboard aircraft or other transport vehicles, due to the extra weight and larger size associated with these types of ovens. They also require a great deal more power consumption due to the use of a separate steam generator system.
Accordingly, particularly when the steam oven is intended for use in a smaller space or in conditions with limited power capacity (such as an aircraft or other transportation vehicles), it is desirable to eliminate the need for using an extra electrical heater or steam generator. Additionally, it has also been found to be desirable to provide an unpressurized steam oven that uses less power, results is lower heat losses, and is more efficient than the currently available steam ovens.